Shaft furnace charging installation

ABSTRACT

A blast furnace charging system for feeding charge material into the hearth of a blast furnace includes at least two hoppers for temporarily storing charge material, each hopper having a discharge assembly for feeding the charge material from the respective hopper into the hearth of a blast furnace, the discharge assembly including an inclined discharge channel having, at its lower end, a material gate providing charge material flow control at the lower end of the discharge channel; and a protection ring arranged in the vicinity of the material gate for leading charge material from the discharge channel to a seal seat of the discharge assembly, where the discharge assembly further includes a heated panel arranged on the protection ring, the heated panel being formed by a panel-like copper body having fluid channels arranged therein so as to form a channel leading from a fluid inlet to a fluid outlet.

TECHNICAL FIELD

The present invention generally relates to a shaft furnace charging installation, in particular to a discharge assembly arranged between a storage hopper and the shaft furnace.

BACKGROUND

While not limited thereto, the present invention is particularly well suited for use in a shaft furnace charging installation of the Bell Less Top™ type as disclosed in U.S. Pat. No. 3,693,812. In this type of charging installation, the furnace is provided with at least two intermediate storage hoppers, which may be alternately opened to ambient atmosphere for loading material therefrom to the interior of the pressurized furnace via a discharge channel. Such furnace charging installations, as shown in U.S. Pat. No. 4,074,835, employ a pair of serially arranged valves between the storage hopper and the furnace. The first valve or material gate performs a material flow control or metering function, by increasing or reducing the area of the storage hopper discharge opening and thereby assists in the achievement of a desired distribution of material on the furnace hearth. The second valve or sealing valve functions to establish a hermetic seal required to permit the alternate pressurizing and depressurizing of the storage hopper.

In the area of the material gate, dust build-up, due to condensation of blast furnace gas in combination with wet equalizing gas and dust particles from the charge material, may occur. Such dust build-up may accumulate on a protection ring and hinder the material gate from properly closing the hopper discharge opening. The limit switch, which indicates that the material gate is in its closed position, may not be activated. The charging sequence is thereby interrupted and is then necessary either to mechanically remove the build-up or to change the limit switch position. The latter can however cause further problems such as excessive wear on the seal on the sealing valve arranged downstream. This is caused by the fact that the material gate is not correctly closed and that a larger gap allows more charge material to leak through the closed material gate.

Also, the dust build-up may be such that, in the closed position of the material gate, the latter rests on the dust build-up, thereby falsifying the weighing results of the charge material fed into the hopper.

In order to avoid such dust build-up, it has been suggested to provide a steam heated panel behind the octagonal chute of the hopper. By heating such a heated panel to a temperature of about 120° C., condensation can be avoided, which means that dust-build-up and its consequences can also be avoided. Such a heated panel consists of a stainless steel casing formed into a shape matching the shape of the octagonal chute. Stainless steel pipes are arranged inside the steel casing and embedded in a heat conductive concrete.

It has been found that the conditions of the blast furnace gas are such that the stainless steel casing and/or the stainless steel pipes quickly corrode and that the heated panel is thereby quickly destroyed and steam is allowed to escape from the stainless steel pipes into the blast furnace or hopper environment.

BRIEF SUMMARY

The invention provides an improved blast furnace charging system, wherein the above drawbacks are avoided.

More specifically, the present invention proposes a blast furnace charging system for feeding charge material into the hearth of a blast furnace, the system comprising at least two hoppers for temporarily storing charge material, each hopper comprising a discharge assembly for feeding the charge material from the respective hopper into the hearth of a blast furnace. The discharge assembly comprises an inclined discharge channel having, at its lower end, a material gate providing charge material flow control at the lower end of the discharge channel; and a protection ring arranged in the vicinity of the material gate for leading charge material from the discharge channel to a seal seat of the discharge assembly. The discharge assembly further comprises a heated panel arranged on the protection ring, the heated panel being formed by a panel-like copper body having fluid channels arranged therein so as to form a channel leading from a fluid inlet to a fluid outlet.

The inventors have found that heated panels made of a panel-like copper body have good corrosion resistance against blast furnace gas, in particular against chlorides in the blast furnace gas. The heated panels according to the present invention therefore have longer lifetime and the risk of steam escaping from the fluid channels is reduced. This leads to a reduced number of maintenance interventions and hence fewer furnace stoppages.

The copper heated panels also provide good heat transfer, enabling the heated plate to be heated to a higher temperature, when compared to the conventional stainless steel heated panels.

The fluid channels in the panel-like copper body may be formed by casting. Alternatively, the fluid channels in the panel-like copper body may be formed by drilling. Plugs may be arranged in the end portions of the drilled fluid channels.

Advantageously, the heated panel has a shape corresponding to the shape of the discharge channel, wherein the panel-like copper body is formed into the shaped heated panel after formation of the fluid channels therein.

The heated panel preferably comprises a connection element for connecting the heated panel to the protection ring.

A wear resistant copper alloy may further be arranged on a lower portion of a front face of the heated panel and on a front face of the connection element.

Preferably, the fluid channels comprise a fluid inlet and a fluid outlet, the fluid inlet and outlet being connected to a fluid circuit for delivering a hot fluid, e.g. steam, to the heated panel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more apparent from the following description of a not limiting embodiment with reference to the attached drawings, wherein

FIG. 1: is a side view of a bell-less top charging system on a blast furnace;

FIG. 2: is an enlarged side view of a portion of a discharge assembly of the system of FIG. 1; and

FIG. 3: is a cross-sectional view through a heated panel of the discharge assembly of FIG. 2.

DETAILED DESCRIPTION

In FIG. 1, reference 10 globally identifies a blast furnace. A Bell Less Top™ charging system 12 of the parallel hopper type uses, in a manner known per se, an angularly adjustable rotary chute 14 for distribution of charge material into the hearth of the blast furnace 10. Two storage or top hoppers 16, 16′ provide temporary storage of the charge material to be distributed by the chute 14. A conveyor belt mechanism 18 provides feeding of the top hoppers 16, 16′ through a feeding assembly 20 arranged above and connected to hoppers 16, 16′. The feeding assembly 20 comprises a collecting cone 22 and a deviation chute 24 for selectively feeding and guiding charge material into either hopper 16 or 16′. Hoppers 16, 16′ are constructed as pressure hoppers to insure that the blast furnace 10 remains sealed from the atmosphere during the charging process. Therefore, hoppers 16, 16′ having an air lock function are each provided with upper and lower sealing valves (not shown).

A discharge assembly or valve block, globally identified by reference 30 communicates with the lower open ends of the hoppers 16, 16′. Discharge cones 32, 32′ at the respective lower open ends of the hoppers 16, 16′ are connected by bellows 34, 34′ to discharge channels 36, 36′. Throttle valves or material gates 38, 38′ provide charge material flow control at the lower ends of the discharge channels 36, 36′. Accordingly, the material gates 38, 38′ enable controlled discharge of charge material from the hopper 16 or 16′ to the rotary chute 14. The material gates 38, 38′ are set by hydraulic drives 40, 40′. Thus, charge material passes from the hoppers 16, 16′ over the discharge channels 36, 36′ to a central feeding spout 42, which directs the charge material vertically onto the rotary chute 14.

FIG. 2 shows in more detail a portion of the discharge assembly 30, showing a discharge channel 36 connected to a discharge cone 32 of a hopper 16. At a lower end 42 of the discharge channel 36, a material gate 38 is pivotably arranged so as to pivot between two positions. In a closed position, as shown in FIG. 2, charge material is retained in the discharge channel 36. In an open position, as shown in dotted lined in FIG. 2, charge material is allowed to flow out of the discharge channel 36 towards the rotary chute 14. The rate of flow of charge material out of the discharge channel 36 can be regulated by setting the material gate 38 in various intermediate positions. A protective casing 44 is arranged around the discharge assembly 30 and has a seal seat 46 for feeding charge material to the rotary chute 14. A sealing valve 48 is associated with the seal seat 46 for sealing the furnace hearth from the hopper 16, thereby allowing the filling of the hopper 16 with charge material without gas pressure drop in the furnace itself.

In the region of the lower end 42 of the discharge channel 36, the charging system 12 comprises a protection ring 50 generally arranged so as to protect the seal seat 46, in particular when the material gate 38 is almost in its closed position.

The protection ring 50 is provided with a heated panel 52 designed and arranged so as to heat at least a portion of the protection ring 50 in proximity to a gate nose 54 of the material gate 38 when the latter is in its closed position. Due to the heated panel 52, the formation of condensation on the protection ring 50 can be avoided. It should be noted that charging material dust is present in the vicinity of the material gate 38. Dust build up, which may otherwise occur due to the condensation of blast furnace gas in combination with wet equalizing gas and dust particles from the charge material, can be avoided.

The heated panel 52 has an upper edge 56 and a lower edge 58. At the upper edge 56, an so-called air canon 60 is arranged for blowing air at very high speed, generally supersonic speed, onto a front surface 62 of the heated panel 52. This air helps to keep condensation and dust particles away from the front surface 62 of the heated panel 52, thereby avoiding accumulation of dust on the protection ring 50.

By keeping the protection ring 50 essentially free from dust build-up, the correct functioning on the material gate 38 can be ensured at least in the sense that the correct closure of the material gate 38 cannot be prevented by such a dust build-up.

Furthermore, the weighing of the charge material in the hopper 16 is adversely influenced if the material gate 38 rests on a dust build-up when in its closed position. By avoiding such a dust build-up, the weighing precision of weighing beams or load cells 64, one of which is shown in FIG. 2, is maintained.

The heated panel 52 itself will now be more closely described by referring to FIG. 3. The heated panel 52 is formed by a panel-like copper body 66 having a front face 62 and an opposite rear face 68, an upper edge 56 and a lower edge 58 and two side edges. Within the panel-like copper body 66, fluid channels 70 are arranged so as to form a channel leading from a fluid inlet 72 to a fluid outlet 74. The fluid inlet and outlet 72, 74 are connected to a fluid circuit (not shown) feeding a hot fluid, generally steam, through the panel-like copper body 66.

The fluid channels 70 may be formed in the panel-like copper body 66 by casting or drilling. Indeed, the panel-like copper body 66 may be formed by casting the copper around a filler material, which can be removed later to reveal the fluid channels 70. Alternatively, the fluid channels 70 may be drilled into the panel-like copper body 66. Interconnecting fluid channels may also be drilled. Channel portions near the upper, lower or side edges of the panel-like copper body 66 may be plugged after drilling. Such channel portions are necessary to form the fluid channels 70 by drilling but need be plugged to form a continuous channel leading from the fluid inlet 72 to the fluid outlet 74.

After formation of the fluid channels 70 in the panel-like copper body 66, the latter is further bent to a shape corresponding to the shape of the distribution channel 36 and material gate 38.

At its lower edge 58, the heated panel 52 comprises an L-shaped connection element 76 for allowing the heated panel 52 to be connected to the protection ring 50. A wear resistant copper alloy may be hard faced onto a lower portion of the front face 62 of the panel-like copper body 66 and onto the connection element 76 for increasing wear resistance on the connection element 76. 

1. Blast furnace charging system for feeding charge material into a hearth of a blast furnace, said system comprising; at least two hoppers for temporarily storing charge material, each hopper comprising a discharge assembly for feeding said charge material from the respective hopper into the hearth of a blast furnace; said discharge assembly comprising: an inclined discharge channel having, at a lower end, a material gate providing charge material flow control at the lower end of the discharge channel; a protection ring arranged in a vicinity of the material gate for leading charge material from said discharge channel to a seal seat of said discharge assembly; and a heated panel arranged on said protection ring, said heated panel being formed by a panel-like copper body having fluid channels arranged therein so as to form a channel leading from a fluid inlet to a fluid outlet.
 2. System according to claim 1, wherein said fluid channels in said panel-like copper body are formed by casting.
 3. System according to claim 1, wherein said fluid channels in said panel-like copper body are formed by drilling.
 4. System according to claim 3, wherein plugs are arranged in the end portions of said drilled fluid channels.
 5. System according to claim 1, wherein said heated panel has a shape corresponding to a shape of said discharge channel, wherein said panel-like copper body is formed into said shaped heated panel after formation of said fluid channels therein.
 6. System according to claim 1, wherein said heated panel comprises a connection element for connecting said heated panel to said protection ring.
 7. System according to claim 6, wherein a wear resistant copper alloy is arranged on a lower portion of a front face of the heated panel and on a front face of the connection element.
 8. System according to claim 1, wherein said fluid channels comprise a fluid inlet and a fluid outlet, said fluid inlet and outlet being connected to a fluid circuit for delivering a hot fluid to said heated panel. 